Influences Of Liquid Motion On The Phase Equilibrium

The main purpose of the present dissertation is to study the influences ofliquid motion on phase equilibrium in macroscopic, especially the absorption-desorption equilibrium and the gas–liquid equilibrium.Principle of phase equilibrium is very significant to unit operation.Thelimit of traditional phase equilibrium is that the rate of mass transfer reachszero on static state. In actual production, the substances are incessantmovement, so the contrary stable condition which the substances may achievemay be different from static phase equilibrium.In the dissertation, the absorption-desorption equilibrium of carbondioxide-water system has been firstly studied. When the saturated solution ofcarbon dioxide flows in the pipeline, solubility of carbon dioxide has beenobserved.Then the gas-liquid equilibrium pressure of ethanol, isopropanoland water have been studied.When liquid is forced to wave with certainfrequency by an oscillator, the pressures have been observed. So the macroexperiment phenomenon may direct the practice.The main experimental results are as follows:1The liquid motion can make the carbon dioxide escape from the saturated solution of carbon dioxide, and achieve a new absorption-desorptionequilibrium. Under different Reynolds number, the desorption degree andtime accord with exponential function. The more carbon dioxide escape fromthe liquid and the less time is needed with higher intensity of turbulence whenachieving the dynamic equilibrium. At16±0.5, about18%dissolved carbondioxide escapes from the system and the solubility of carbon dioxidedecreases to37.40mol·m-3. Under Reynolds number4.5×104, the dynamicsolubility of carbon dioxide decreases to41.23mol·m-3and the maximumdesorption degree is13%at11±0.5, but at14±0.5the dynamic solubilityof carbon dioxide decreases to37.01mol·m-3and the maximum desorptiondegree is17%. The dynamic absorption-desorption equilibrium of carbondioxide-water system still accord with that low temperature is helpful toabsorption.Under Reynolds number3.8×104, the dynamic solubility of carbondioxide decreases to35.65mol·m-3and the maximum desorption degree is15%by reverse at16±0.5, but the solubility of carbon dioxide decreases to35.07mol·m-3and the maximum desorption degree is16%by corotation at thesame temperature. The result shows that the desorption ability of pipeline ishigher than that of pump.2The oscillation of liquid can make gas-liquid equilibrium pressures ofethanol, isopropanol and water away from saturation pressures. The pressuresabove liquid level increase and stop rising within about3minutes. Underdifferent oscillation frequency, the deviation degree and time accord with exponential function. Under210min-1, the differential pressure of ethanol is1996Pa and the maximum deviation degree is14.5%at35. At differenttemperature, the deviation degree of material is different under the sameoscillation frequency. The deviation degree would be bigger with highertemperature. Under130min-1, the deviation degree of ethanol is3.9%at30and is6.3%at35. The dynamic gas-liquid equilibrium still accord with thathigh temperature is helpful to evaporation. At the same reduced temperature,different materials have different the deviation degree. Under130min-1, thedeviation degree of ethanol is6.3%and the deviation degree of isopropanol is5.1%at the reduced temperature0.59. The logarithm of a dynamic gas-liquidpressure and the reciprocal of temperature have a very good linearrelationship.3Flow rate can make either the absorption-desorption equilibrium ofcarbon dioxide-water system or the gas-liquid equilibrium away fromprimitively static equilibrium. On the condition of liquid motion, engineeringcalculation or designing should consider the influence of flow rate.